Allylic and vinylic compounds can be polymerized via a free radical addition process. However, while vinyl monomers (e.g., acrylamide, acrylic acid, acrylic acid esters, vinylamine) can be easily polymerized to obtain polymers of suitable size and in high yield, the same is not true for allylic monomers. The difficulty encountered with the polymerization of allylic monomers is due primarily to the stability of allyl radicals relative to vinyl radicals. Consequently, an initiating radical often abstracts a H-atom from the allylic monomer rather than adding to the C.dbd.C bond, resulting in a competing self-termination reaction between the allylic hydrogen atoms and the initiating free radical often referred to as allylic degradative chain transfer. The same difficulties are encountered when allylic monomers are copolymerized with vinylic monomers. Thus, to polymerize allylic monomers large quantities of a free radical initiator are usually required, resulting in the production of low molecular weight polymers which comprise relatively high quantities of terminal catalyst residues. Polymers of allylamines (e.g., allylamine, diallylamine, triallylamine) are particularly difficult to prepare due to a further decreases the reactivity of the allylic bond in polymerization reactions and unwanted side-reactions, both resulting from the presence of the amino functionality.
Several processes for polymerizing allylamine which use cationic water soluble diazo free radical initiators and/or additives such as multivalent metal ions are known (see, for example, U.S. Patent Nos. 4,504,640, 4,540,760 and 4,528,347, to Harada et al.; 4,927,896 to Blocker et al.). However, improvements in the current processes for polymerizing allylamine are needed. For example, the cationic charge on a diazo free radical initiator can improve the solubility of the compound in water. However, the ionic charge can also destabilize the radicals generated upon decomposition of the initiator and thus may adversely affect the process (e.g., result in polymers having high polydispersity). Furthermore, regulators or additives (e.g., multivalent metal ions) can be difficult to remove from the final polymer products and can render the polymer unacceptable for many uses, such as in the pharmaceutical industry.
A need exists for a process for polymerizing allylic amine compounds which reduces or eliminates the referenced problems.